P0116: Engine Coolant Temperature Sensor Circuit Range/Performance
P0116 means the engine computer sees a coolant temperature reading that is electrically valid but does not make sense, most often a sensor reading too warm after the engine has sat for hours. It is usually not urgent, but it turns on the check engine light and can affect cold starts, fuel use and emissions.
You can drive, but get it checked soon
Limp mode is not expected with this code, and many cars show no symptoms. A wrong coolant reading can still cause hard cold starts, rough idle and higher fuel use, so have it checked soon rather than ignoring it.
What it means
The coolant temperature sensor is a thermistor, a sensor whose electrical resistance changes with temperature. The engine control module sends it 5 volts through a resistor, and as the coolant warms, the sensor's resistance and the signal voltage fall. The module uses this value for cold-start fuel enrichment, idle speed, ignition timing, the radiator fan and the switch to closed-loop mixture control, where it adjusts fuel using the oxygen sensors. P0116 is a plausibility fault, so the signal is within the normal electrical range but does not match what the module expects. The most common check compares coolant temperature with intake air temperature after the engine has sat for many hours, when the two should be close. On some Ford engines the module measures cylinder head temperature and calculates a coolant value from it. Ford diesels instead check whether the coolant warms up fast enough in freezing weather. A sensor stuck reading warm can reduce cold-start enrichment and defeat the thermostat monitor, which is why emissions rules require this test. Depending on the engine, GM may set the code after one or two trips.
Likely causes
- Sensor drifting and reading too warm (ageing, coolant ingress)Very likely
A sensor that reads warmer than the real coolant temperature after a long cold soak fails the comparison with intake air temperature.
- Corrosion or contact resistance in connector or wiringPossible
Extra resistance in the circuit changes the signal voltage and can make the coolant look warmer or cooler than it is.
- Block heater or preheater not detectedPossible
If a block heater warmed the coolant and the module did not detect it, the warm reading looks implausible against cold air.
- Comparison sensor (intake air, ambient) wrongLess likely
The test compares coolant with other temperature readings, so a faulty intake air or ambient sensor can cause a false fail.
- Control module calibrationLess likely
The module's stored software may be set up in a way that triggers the check wrongly, though this is uncommon.
What you may notice
- Check engine light on
- Poor cold start (too little enrichment)
- Higher fuel consumption or idle problems
- Often no noticeable symptoms
What to check, cheapest first
- 1Think about whether a block heater or coolant preheater was plugged in before the code appeared, since that can warm the coolant and cause a false reading. · you can do it
- 2Inspect the coolant temperature sensor connector and wiring for corrosion, looseness, damage or coolant leaking into the plug. · you can do it
- 3Check the coolant level and look for coolant leaking around the sensor. · you can do it
- 4Read live data with a scan tool after the car has sat for several hours and compare coolant temperature with intake air temperature; they should be close. · mechanic
- 5Measure the sensor's resistance and the signal voltage, and compare them with the specification for the temperature. · mechanic
- 6Replace the sensor if it reads wrong, clear the code, and run a drive cycle to confirm the repair. Check for a software update if the fault returns with a good sensor and wiring. · mechanic
Related codes
Frequently asked questions
Can I drive with a P0116 code?+
Usually yes for a short time. Limp mode is not expected, but cold starting, idle and fuel use can suffer, so get it checked soon.
Can a gas cap cause P0116?+
No. The code concerns the coolant temperature reading, not the fuel system or evaporative system, so the gas cap is not a cause.
Will P0116 pass an emissions test?+
Probably not. The code is emissions-relevant and keeps the check engine light on, which normally fails an inspection until it is repaired and the code is cleared.
Can I fix it myself?+
Often yes. Repair is rated easy and typically takes about 0.3 to 1.5 hours, usually by replacing the sensor or cleaning a connector.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10